1. Field of the Invention
This invention concerns measurement of internal volumes, and more particularly measurement of the net internal volume of successive test pieces containing unknown amounts of a liquid. Such measurements are useful in the determination of the amount of liquid to be added to bring the liquid to a prescribed level, as in filling transmissions during automobile assembly operations which transmissions contain an unknown residual volume of transmission fluid from previous testing operations.
2. Description of the Prior Art
It has heretofore been known to measure the internal volume of a receptacle by connecting a reference vessel pressurized with compressed air to the unpressurized interior of the receptacle, and allowing the compressed air to expand into this interior space of the receptacle. The final pressure level thereafter subsisting in the space comprised of the interior of both the receptacle and the reference vessel is related to the beginning pressure in the same proportion that the volume of the reference vessel bears to the total volume of the connected reference volume and receptacle, as stated by Boyle's Law. Since the volume of the reference vessel is known as well as the "dry" volume of the receptacle, the precise net volume of the receptacle with an unknown volume of liquid may be computed.
Such a method assumes that no leaks exist, since the presence of such leaks would invalidate the calculations due to the loss of pressurized fluid during the test, causing the final pressure to be lower than if no leaks existed.
As noted, the above basic method has been applied to measure the volume of residual transmission fluid in transmissions during automotive assembly operations. In applying the method, the various outlets are sealed, i.e., tachometer, vent, cooler lines, etc., and a connection made to the reference tank, typically to the filler tube.
Imperfect sealing of the openings sometimes occurs during this procedure, and slight leakage may also occur through the transmission housing joints or at various other points such as past the transmission shaft seals.
The present invention enables the effects of such leaks on the volume measurement to be corrected to produce accurate measurement despite the presence of small leaks.